1. Field of the Invention
The present invention relates to a plasma processing apparatus used in semiconductor manufacturing.
2. Description of the Related Art
Plasma processing apparatuses that generate plasma by propagating microwaves from slots formed in a Radial Line Slot Plate (Radial Line Slot Antenna: RLSA) into a processing container are conventionally used in the manufacturing field of semiconductor devices (for example, refer to Patent Document 1). These RLSA-type plasma processing apparatuses are capable of forming uniform plasma having high density and a low electron temperature, and performing plasma-process of large-sized semiconductor wafers uniformly and fast. A well-known example of the plasma process is a process of etching a surface of a substrate by using a CF-based gas or a CFH-based gas.
In the plasma processing apparatuses, the microwaves are propagated into the processing container through a dielectric material disposed on a ceiling surface of the processing container. Then, a process gas introduced to the processing container is plasmatized by energy of the microwaves, and thus etching is performed on the surface of the substrate. Generally, an introducing unit for introducing the process gas to the processing container is disposed, for example, on a side surface of the processing container. Also recently, in addition to the introducing unit disposed on the side surface of the processing container, an introducing unit for introducing the process gas is formed on the ceiling surface of the processing container. Accordingly, improvement in the uniformity of etching on the surface of the substrate (Radical Distribution Control (RDC)) is obtained by optimizing a ratio of an amount of a process gas introduced from the introducing unit on the side surface to an amount of a process gas introduced from the introducing unit on the ceiling surface.    (Patent Document 1) Japanese Laid-Open Patent Publication No. 2009-99807
However, in a conventional plasma processing apparatus, a carbon-based product may be generated and adhered to an introducing unit for introducing a process gas to a processing container. Also, the process gas may be unable to be smoothly introduced to the processing container as a gas ejection hole formed in the introducing unit is blocked by the adhered product. When the gas ejection hole is blocked by the adhered product, a balance between the amounts of process gases introduced from an introducing unit on a side surface and an introducing unit on a ceiling surface may change, and thus etching uniformity over a surface of a substrate may deteriorate. Moreover, an operation of solving a blocking of the gas ejection hole is troublesome, and thus maintenanceability is deteriorated.